1. Field of the Invention
The present invention relates to a method for measuring the fine change in the dynamical characteristics of the middle ear, the measuring apparatus and the method for indicating the result of the measurement of the dynamical characteristics of the middle ear.
2. Description of the Prior Art
This kind of probe for measuring the dynamical characteristic of the middle ear was disclosed in Japanese Utility Model Publications Nos. 60-168805 and 60-168806. According to these publications, three pieces of stainless steel tubes are passed and fixed to the inside of a member to be inserted into the external auditory meatus; the projected ends of said tubes are respectively connected to the sillicon tubes which communicate with a microphone, an earphone for probe and an earphone for stimulation respectively; and a pressure tube is branched from the tube communicating with the earphone for stimulation to constitute a probe for measuring the dynamical characteristics of the middle ear.
In the case of the above-mentioned conventional probe, however, the insertion member of the probe is connected to the microphone and the earphone with considerably long tubes such as those of 15-22 cm long. As indicated by the solid line, A.sub.1 in FIG. 3, the theoretical characteristic of the sound pressure measured by the probe with one end of which is closed is almost flat to the change of the frequency. On the other hand, as indicated by the solid line A.sub.2 in FIG. 4, the theoretical characteristic of the phase difference is preferred to increase linearly to the change of the frequency. When the long tubes are used like the case of said conventional probe, however, the acoustic resonance in the tube is relatively small, so that both the sound pressure curve based on the measured value and the phase difference characteristic vary largely with the frequency within the range of the audible frequency as indicated respectively by the broken line C.sub.1 in FIG. 3 and by the broken line C.sub.2 in FIG. 4, and these are the problems of the conventional probe. Even among the conventional probes, there are some with the tube length reduced to several centimeters, but such tube length is still too large; the tube is made from the soft material such as the vinyl; the wall thickness of the tube is too small; and the body of the probe is made from the soft material such as the plastic, so that the mechanical resonance point is low. As a result, the peak values of the sound pressure characteristic and the phase difference characteristic within the audible frequency range remain at undesirable high levels respectively. Thus, the conventional probes are unable to measure the fine frequency characteristic of the human eardrum.
The present invention provides a middle ear dynamical characteristics measuring apparatus not only capable of measuring the fine frequency characteristic of the human eardrum but also capable of three-dimensionally indicating the result of the measurement by this measuring apparatus so that even those who are lacking in the knowledge of the dynamics will be able to utilize for general diagnosis.
The further objects and characteristics of the present invention will be clarified by the following descriptions.